"I'm not married to HDTracks, I just don't know if there's a better site that has the same amount of variety."
I had some problems in the past with HD Tracks downloads on Mac - not this particular problem though. Generally I don't care for HD Tracks and their download scheme. Also, being from Canada, the rotten current exchange rate on our dollar makes purchases a poor value proposition (not to mention the limited selection due to country copyright restrictions). Also, hate the fact that you can't purchase individual album tracks - required to buy the whole album.
My current go to site is 7digital (www.7digital.com
). They have a native site for Canada with billing in local currency (not sure how things work from a US IP address). Decent selection of CD quality (16/24 bit 44.1/48kHz) selections in predominately FLAC format (also have some MQA). Not so much available in higher sample rate stuff.
The big feature for me is the option to be able to download individual tracks - rarely purchase the whole album. Downloads come in the form of a ZIP file (no proprietary download software here) and have worked flawlessly. Your purchases are permanently available under the "My Music" tab can be accessed at any time for a "re-download" should anything happen to your original file.
Here's a review; https://www.whathifi.com/7digital/review
Sorry I can't help with your HD Tracks download issue but I have moved on from my limited past experiences with them and highly endorse 7digital.